Abstract: Objective: To detect the bacterial components in periapical lesions of deciduous teeth and analyze the relationship between the bacterial flora and clinical symptoms. Methods: 31 periradicular lesion samples of deciduous teeth diagnosed as periapical periodontitis were collected. DNA was extracted and analyzed using 16S rDNA cloning and sequencing for identification of bacteria. Chi-square was chosen to compare the detection rate of bacteria with different symptoms, including spontaneous pain, chewing pain and sinus. Results: 268 phylotypes from 2057 clones were identified belonging to nine phyla. The three most prevalent bacteria, Fusobacterium nucleatum (74.19%) , Dialister invisus (67.74%) and Campylobacter gracilis (64.52%)showed no relationship with any symptoms. Prevotella tannerae was detected to significantly increase in samples with spontaneous pain, so did Prevotella oris and Haemophilus parahaemolyticus in the group of chewing pain, and Prevotella nigrescens, Eubacterium brachy in samples with sinus. Two uncultured Veillonella sp. were significantly fewer in the samples of chewing pain. Conclusion: Periapical lesions in deciduous teeth contained polymicrobial. Prevotella, Eubacterium and Veillonella had certain relations with clinical symptoms.